How to make the top of candy mountain from Kirby super star
I thought it would be easy, but as this object is both smooth and sharp, it is not. Maybe there's a easiest way to dot it, anyway here is mine:


Create a plane and subdivide it vertically (for example 7 times).
Give it an Array modifier and, in Count, choose the number of duplications (i.e. the number of spikes you'll need), for example 12. Enable the Merge and First/Last options.
Create an Empty at the origin point of your plane.
Give your plane a SimpleDeform modifier with the Bend option enabled and choose the Empty as Axis, Origin.
In the same modifier, choose 360° as Deform Angle . Now your shape is a ring.
Give your plane a Subdivision Surface modifier, and Smooth it in the T panel.
In Edit mode begin to move up and down your vertices so that it creates spikes. Move some vertices along their edges to sharpen the top and bottom of those spikes. Now you have a kind of crown.
Keep a copy of this object + Empty.
Apply the Array modifier, then apply the SimpleDeform modifier. Keep the Subsurf.
You need to make some corrections to join the first and the last object of the Array (maybe the gap is avoidable, I don't know), use alt M to merge vertices.
Now you can begin to extrude and scale the top, then close it with a alt M.
You can give your object a Solidify modifier if you want to give it thickness